1. Field of the Invention
This invention relates to dry spreadable compositions; their use as carriers of bioactive materials; and methods for preparing and using said compositions. More specifically, the invention relates to surfactant-diatomaceous earth compositions for agricultural use in the form of dry spreadable granules and methods of preparing same, and even more specifically for their use in the broadcast delivery of pesticides to the soil.
2. Description of Prior Art and Problems
An organic pesticide is a bioactive material which destroys or inhibits the action of plant or animal pests. The general term pesticide includes insecticides, herbicides, fungicides, plant growth regulators, rodenticides, and miticides.
Organic pesticides are widely used in soil and turf by both consumers and commercial operators. Pesticide compounds may be used alone; however, usually they are formulated into conventional forms such as dust, granule, microgranule, wettable powder, flowable powder, emulsion, microcapsule, oil, aerosol, etc., using techniques well known in the art. To improve or stabilize the effects of the pesticide, the pesticide is blended with suitable adjuvants and then used as such or after dilution if necessary. Examples of adjuvants include carriers, diluents, spreaders, emulsifying agents, wetting agents, dispersion agents, or fixing agents.
The present invention is directed towards dry spreadable diatomaceous earth granules, and towards methods of preparing such granules, which can be applied with a dry spreader to a target area and, when exposed to water via, for example, rain or irrigation, will not only readily disintegrate, but actively spread on solid substrates so as to achieve disintegration area diameter to original granule diameter ratios larger than that heretofore realized. These dry spreadable granules are primarily used as carriers for bioactive materials such as pesticides and are easy to formulate, ship, store, and apply.
This invention provides dry spreadable compositions; their use as carriers of bioactive materials; and methods for preparing and using said compositions. Specifically, the invention relates to surfactant-diatomaceous earth compositions in the form of dry spreadable granules and methods of preparing same, and more specifically to their use in the broadcast delivery of pesticides to the soil.
The granules utilize, in addition to the diatomaceous earth, a surfactant composition designed to provide binding, rewetting and disintegration properties to the granules.
The instant invention relates to the discovery of a granule which can function as a carrier for pesticides or fertilizers in a broadcast or dry spreading application. Granules for such a use have to possess certain specific characteristics which are not necessary or critical in compositions designed for admixing in large volumes of water such as tank mixes and ultimately sprayed upon sites to be treated. Bioactive-carrier compositions are often referred to as wettable powders, water dispersible granules, etc. as opposed to the dry spreadable or broadcast granules of the instant invention. Characteristics which are specific to dry spreadable granules include hardness and an ability to maintain integrity upon normal, commercial handling in a dry spreading operation and yet be capable of quickly disintegrating or scattering upon what may be a minimal exposure to water, such as, for example, a light rain.
This ability to disintegrate or scatter on a solid substrate can be primarily measured by the xe2x80x9cDisintegrationxe2x80x9d test, as described herein, which measures what happens to a typical granule when a drop of water lands on it. Essentially, the disintegration is observed and recorded by measuring the area covered by the granule composition after being exposed to a drop or drops of water compared to the area covered by the original dry granule. Of course, the higher the ratio, the more efficacious the delivery of the bioactive that is being carried by the granule.
Once the granule has been disintegrated or scattered by the droplet, the characteristics common with the water dispersible products also come into play such as the composition""s ability to disperse in large volumes of water and this property can be measured via tests such as the xe2x80x9cBreakupxe2x80x9d test as also described herein.
The instant invention relates to the discovery of a dry spreadable diatomaceous earth granule which, when exposed to water on a solid substrate, has a high disintegration area diameter to original granule diameter ratio. As a result, when the granules of this invention are broadcast upon the locus to be treated, e.g., soil, and then water treated, the area affected by the granule formulation is much enhanced over that realizable when the dry spreadable granules of the prior art are similarly broadcast.
By diatomaceous earth is meant a silica material characterized by a large surface area per unit volume. This is the result of an enormous number of fine pores within the structure. Diatomaceous earth is a naturally occurring material and consists mainly of accumulated shells or frustules of intricately structured amorphous hydrous silica secreted by diatoms. Diatoms are single-celled golden brown algae of the Bacillariophyceae class. The enhanced absorption/adsorption properties of the diatomaceous earth result from the very large internal surface area.
The effective diatomaceous earth of this invention has a surface area in the range of from greater than about 5 square meters per gram to less than about 90 square meters per gram, preferably from greater than about 10 to less than about 60 square meters per gram and a pore volume in the range of from greater than about 2 cubic centimeters(cc)per gram, to less than about 5 cc per gram, preferably from greater than about 3 cc per gram to less than about 4 cc per gram. Natural diatomaceous earth is preferred for this invention.
Diatomaceous earth is present in the granule composition at from about 35 to about 95 weight percent, preferably from about 50 to about 95 weight percent of the total diatomaceous earth, surfactant, and pesticide granule composition.
The surfactant composition of the present invention is present at from about 5 to about 40 weight percent, preferably from about 5 to about 20 weight percent of the total diatomaceous earth/surfactant/pesticide granule composition. The surfactant composition provides three essential properties to the dry spreadable granules.
First, the surfactant composition must act as a binder for the particles in the granule so that after the processing and agglomerating water used in the initial preparation of the granule has been driven off, residual surfactant will act as a binder to form a reasonably hard, easily handleable, i.e., a non-dusty, dry spreadable granule.
Second, the surfactant composition must possess a good rewetting ability such that when the granule is applied to the site to be treated and subsequently exposed to water, the surfactant composition will enable the water to easily penetrate the interstices of the individual diatomaceous earth particles quickly, i.e., xe2x80x9cwetxe2x80x9d the internal surface areas of the particles. It is theorized that this rapid rewetting of the internal surfaces results in a displacement of the air initially entrapped within the particles which then provides an additional scattering mechanism for the granules of this invention.
Third, the surfactant composition must be able to aid in the breaking up and rapid spreading of the particles initially in the granule.
In summary, the surfactant composition should possess the characteristic properties of being a good binder, rewetting agent, and disintegration aid. These properties could, of course, be found to a limited extent in a single component surfactant composition, but preferably at least a two-component composition is utilized. As will be noted below, polymeric dispersants, i.e., those with repeating units or bulky dispersants often can function as acceptable binders. A three-component surfactant composition in which each surfactant is optimized for one of the aforementioned, desired properties of the composition is most preferred.
The disintegration aids of the instant invention are usually present at from about 3 to about 15 weight percent; preferably from about 6 to about 10 weight percent based on the weight of the diatomaceous earth, surfactant, and pesticide granule composition. Certain nonionics can function as disintegration aids, preferably high molecular weight materials with repeating units, i.e., the polymerics. However, the most preferred disintegration aid surfactants of this invention are the solid (at room temperature, i.e., 24xc2x0 C.), high molecular weight, polymeric anionic surfactants.
The rewetting agents of the instant invention are usually present at from about 2 to about 15 weight percent, preferably from about 2 to about 3 weight percent based on the weight of the diatomaceous earth, surfactant, and pesticide granule composition. Certain nonionics can function as rewetting agents, preferably the low molecular weight materials, i.e., the non-polymerics. However, the most preferred rewetting surfactants of this invention are the lower molecular weight, non-polymeric anionic surfactants. These surfactants are selected for their ability to move more quickly in aqueous environments than those anionics used as disintegration aids.
The binders for use in the granules of this invention, are usually present from about 0 to about 10 weight percent, preferably from about 2 to about 6 weight percent based on the weight of the diatomaceous earth, surfactant, and pesticide granule composition. These binders can be traditional binders well known in the art such as the starches, the sugars, etc., but preferably the granules of this invention use residuals or the secondary characteristics of the disintegration aids and/or rewetting agents described herein as the binding agents.
The anionics useful in the surfactant compositions of this invention include the alkyl and alkyl ether sulfates. These materials have the respective formulae ROSO3M and RO(C2H4O)xSO3M wherein R is an alkyl, alkenyl or alkylauryl group of about 8 to about 22 carbon atoms, x is 1 to 10, preferably 1 to 4, and M is a water-soluble cation such as ammonium, sodium, potassium, magnesium, triethanolamine (TEA), etc. The alkyl ether sulfates useful in the present invention are condensation products of ethylene oxide and monohydric alcohols having about 8 to about 22 carbon atoms. Specific examples of the above sulfates include ammonium lauryl sulfate, magnesium lauryl sulfate, sodium 2-ethyl-hexyl sulfate, sodium actyl sulfate, sodium oleyl sulfate, sodium tridecyl sulfate, triethanolamine lauryl sulfate, ammonium linear alcohol, ether sulfate ammonium nonylphenol ether sulfate, and ammonium monoxynol-4-sulfate.
Another suitable class of anionic surfactants are the water-soluble salts of the general formula:
R1xe2x80x94SO3xe2x80x94M
wherein M is a water-soluble cation and R1 is selected from the group consisting of:
i) a straight or branched chain, saturated aliphatic hydrocarbon radical having from 8 to 24, preferably 12 to 18 carbon atoms;
ii) a mono-, di-, or tri- C1-C6 alkyl substituted aryl wherein the aryl is preferably a phenyl or naphthyl group;
iii) alpha-olefins having 12 to 24 carbon atoms, preferably 14 to 16 straight chain carbon atoms, most preferably 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, and 1-tetracosene; and
iv) naphthalene-formaldehyde condensation products.
Specific examples include Supragil MNS/90, a trademark of Rhodia Inc. for an alkylnaphthalenesulfonate-formaldehyde condensate and Supragil WP, a trademark of Rhodia Inc. for a non-polymeric alkylnaphthalenesulfonate.
Additional examples of anionic synthetic surfactants which come within the terms of the present invention are: i) the isethionates, i.e., the reaction products of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil; and ii) the n-methyl taurates, i.e., the sodium or potassium salts of fatty acid amides of methyl tauride in which the fatty acids, for example, are derived from coconut oil. Other anionic synthetic surfactants of this variety are set forth in U.S. Pat. Nos. 2,486,921; 2,486,922; and 2,396,278, which are incorporated herein by reference.
Still other anionic synthetic surfactants include the classes designated as the sulfosuccinates and sulfosuccinamates. These are of the general formulae: 
wherein R2 is a C2-C20 alkyl or alkylamido. These classes include such surface active agents as disodium N-octadecylsulfo-succinamate; tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfo-succinamate; diamyl ester of sodium sulfosuccinic acid; dihexyl ester of sodium sulfosuccinic acid; and dioctyl esters of sodium sulfosuccinic acid.
Another class of anionic organic surfactants are the B-alkyloxy alkane sulfonates. These compounds have the following formula: 
where R3 is a straight chain alkyl group having from 6 to 20 carbon atoms, R4 is a lower alkyl group having from 1 to 3 carbon atoms, and M is a water-soluble cation as hereinbefore described.
Specific examples of B-alkyloxy-alkane-1-sulfonates, or alternatively 2-alkyloxy-alkane-1-sulfonates include: potassium-B-methoxydecanesulfonate, sodium 2-methoxy-tridecanesulfonate, potassium 2-ethoxytetradecyl-sulfonate, sodium 2-isopropoxyhexadecylsulfonate, lithium 2-t-butoxytetradecylsulfonate, sodium B-methoxyoctadecylsulfonate, and ammonium B-n-propoxydodecylsulfonate.
Also to be included in the anionic class of surfactants are the disulfonates of the general formula: 
wherein R5 is a C8-C20 alkyl group and M is a water-soluble cation as hereinabove described. The preferred anionics of the disulfonate class are disodium dodecyl diphenyloxide disulfonate and ethoxylated nonylphenyl ammonium disulfonate. All of the above-described anionic surfactants and mixtures thereof may or may not be ethoxylated with from about 1 to about 10 ethylene oxide units per xe2x80x9cRxe2x80x9d unit.
Also useful as a disintegration aid surfactant for the granules of the instant invention are the alkali and alkali earth metal salts of the lignosulfonates.
Illustrative of the nonionics which are useful in the surfactant compositions of this invention include the following:
A) Amides such as:
i) alkanolamides of the formula 
xe2x80x83wherein Rxe2x80x2 and Rxe2x80x3 each can be xe2x80x94H, xe2x80x94CH2CH2OH, or xe2x80x94CH2xe2x80x94CHxe2x80x94OH; 
ii) ethoxylated alkanolamides of the formula 
iii) ethylene bisamides of the formula 
B) Esters such as:
i) fatty acid esters of the formula 
ii) glycerol esters of the formula 
iii) ethoxylated fatty acid esters of the formula 
iv) sorbitan esters of the formula 
v) ethoxylated sorbitan esters of the formula 
C) Ethoxylates such as:
i) alkylphenol ethoxylates of the formula 
ii) alcohol ethoxylates of the formula
Rxe2x80x94Oxe2x80x94(CH2CH2O)nH;
iii) tristyrylphenol ethoxylates of the formula 
iv) mercaptan ethoxylates of the formula
Rxe2x80x94Sxe2x80x94(CH2CH2O)nH
D) End-capped and EO/PO block copolymers such as:
i) alcohol alkoxylates of the formula 
ii) ethylene oxide/propylene oxide block copolymers of the formula 
iii) copolymers of the formula 
iv) chlorine capped ethoxylates of the formula
Rxe2x80x94(OCH2CH2)xCl; and
v) tetra-functional block copolymers of the formula 
xe2x80x83wherein
R is a fatty alkyl group, preferably a C6-C22 fatty alkyl group, most preferably a C8-C18 fatty alkyl group;
R1 is xe2x80x94H or a fatty alkyl group, preferably xe2x80x94H or a C6-C22 fatty alkyl group, most preferably xe2x80x94H or a C8-C18 fatty alkyl group;
x, xxe2x80x2, y, yxe2x80x2 and n are each independently moles of ethylene oxide preferably 1 to 300; most preferably 1 to 150; and
m, mxe2x80x2, l and lxe2x80x2 are each independently moles of propylene oxide, preferably 1 to 300; most preferably 1 to 150.
Among the preferred disintegration aids are: the water soluble salts of alkylnaphthalenesulfonate-formaldehyde condensates; sodium lignosulfonate, diphenyloxide, ethoxylated tristyrylphenols, ethoxylated tristyrylphenol phosphates, the ethylene oxide/propylene oxide block copolymers, and acid, salts and copolymers of the polyacrylates.
Among the preferred rewetting agents are: the alkylnaphthalenesulfonates, sodium methyloleoyl taurate, the sulfosuccinates, the carboxylates, the alkylarylsulfonates, the ethoxylated alkyl phenols and the ethoxylated alcohols.
Although electrostatic disintegration aids such as the anionics are preferred, steric disintegration aids such as the polyvinyl alcohols can also be used.
Although the dry spreadable granules of this invention can be prepared by a standard pan granulation process, it is preferred that the granules, with or without the presence of a pesticide, are prepared via a homogeneous extrusion process. Of note, granules that are prepared in the absence of a pesticide by the homogeneous extrusion process can subsequently be sprayed with pesticide to adhere same to the granules.
The extrusion granulation process is illustrated as follows: First, each component is weighed, combined, and blended. Water is then added with continuous mixing until from about 10 to about 50 weight percent, preferably about 25 to about 45 weight percent moisture content is realized. The mixture is then fed to a low pressure basket or radial extruder. The wet mass is extruded through a die having openings with diameters of from about 0.8 mm to about 2.0 mm, preferably about 1 mm. The extrudate is then fed to a vibratory fluidized bed dryer which reduces the moisture content to below about 5; preferably to below about 4 and most preferably below about 2.5 weight percent; the weight percents being based on the total weight of the composition at that respective step in the process.
In the spray formulation process, diatomaceous earth/surfactant granules are prepared by the homogeneous extrusion process described above, and the pesticide is dissolved in an appropriate solvent, e.g., iso-propanol or xylene in an amount sufficient to make a suitably viscous sprayable solution, typically from about 10 to above about 50 percent by weight pesticide and sprayed onto the granules. It is also recognized that certain actives can be melt sprayed onto the granules. The spray is continued onto the granules with continuous mixing. The sprayed granules are then dried, preferably in a fluid-bed dryer to final moisture content as indicated above. The product, however made, is then sieved in a particle classifier to remove oversized and undersized granules. It is preferred that the final product is that which passes through a 10 mesh screen but will not pass through a 60 mesh screen.
A serendipitous and unusual characteristic of the diatomaceous earth granules of this invention, which are designed to be broadcast or dry spreadable, is the speed with which these granules will disperse in water. When the granules of this invention with size of 1xc3x975 (diameterxc3x97length in millimeters) are gently placed on the surface of cold tap water (about 20xc2x0 C.) in, for example, a beaker, the granules, with no mechanical energy input, will completely disintegrate within two (2) to ten (10) seconds. Most conventional water dispersible granules require from five (5) to thirty (30) or more inversions of the beaker to effect a similar result in a similar time period.
As indicated above, a further preferred embodiment of the present invention is the use of the granules described above as a carrier for the broadcast delivery of pesticides, e.g., insecticides, herbicides, fungicides and plant growth regulators. For the purpose of expediency, the term xe2x80x9cpesticidexe2x80x9d herein is also defined to include fertilizers such as urea. Specifically, the present invention is directed towards a granule as described above, methods of preparing said granules, use of said granules as a carrier to broadcast pesticides, and the pesticidal granule per se.
Although the instant invention is universally applicable to all pesticides, the preferred classes of pesticides include the pyridines, carbamates and dithiocarbamates, chlorinated hydrocarbons, organophosphorous compounds, dinitroanilines, diphenyl ethers and synthetic pyrethroid compounds.
Other well known specific pesticides include oxidiazon, iprodione, aluminum salt of ethyl hydrogen phosphonate, (fosetyl Al), and those described in U.S. Pat. No. 5,317,834 which is incorporated herein by reference.
In this embodiment, the pesticide is present in the granule described above, in an effective amount that will not interfere with the desired properties of the granules, i.e., the dry spreadability. For example, the pesticide must not be present in an amount that would result in xe2x80x9cstickyxe2x80x9d granules which cannot be dry spread.
Commercial water-dispersible pesticide granules (WDGs) usually contain relatively high loadings of the pesticidal active because they are designed to be added to, and therefore significantly diluted with water and the resulting aqueous solution/suspension sprayed upon the locus to be treated. The granules of the instant invention, on the other hand, are designed to be dry spread directly on the locus to be treated and thus usually contain relatively lower levels of pesticidal active than the WDGs.
Although, in the present invention, the pesticide may be present up to about 60 weight percent, the pesticide is preferably present at from about 0.005-30 weight percent, most preferably 0.5-20 weight percent, based upon the total weight of the diatomaceous earth, surfactant, and pesticide in the granule.
The granules, containing the pesticide can be broadcast, that is, applied with a dry spreader to a target area and, when exposed to water via, for example, rain or irrigation, readily decompose or disintegrate and actively spread. The highly active disintegration process allows the pesticide to be delivered over a larger surface area than that immediately covered by the original granules resulting in a much more effective delivery of the pesticides to the targeted area.